1. Technical Field
The present disclosure relates to an Inductively Coupled Plasma (ICP) emission spectrometer for analyzing elements (for example, trace impurity elements) contained in a solution sample.
2. Description of the Related Art
An ICP emission spectrometer atomizes or ionizes a solution sample for ICP emission spectroscopy by using inductively coupled plasma (ICP), and performs a spectroscopy analysis on atomic emission lines (spectral lines) emitted at that time so as to perform a quantitative analysis and a qualitative analysis on trace impurity elements. Then, the ICP emission spectrometer identifies elemental species from a wavelength of a detected atomic emission line, and calculates concentration of trace elements based on intensity thereof. However, the intensity of the atomic emission line varies depending on the elemental species or element-containing concentration, and even the same element has the atomic emission line of various wavelengths. Accordingly, the intensity varies depending on which atomic emission line is selected. Furthermore, characteristics of the ICP emission spectrometer show that detection efficiency varies depending on the wavelength of the atomic emission line. An ICP emission spectrometer is known which can accurately analyze a wider concentration range for much more elements (for example, refer to JP-B-H06-68467 and JP-B-H06-68468).
JP-B-H06-68467 discloses a photometric device for emission spectroscopic analysis which includes means for changing an amplification degree of a photomultiplier by comparing a detection output of the photomultiplier with a reference value and by feeding back a comparison output to an application voltage of the photomultiplier, and means for calculating a photometric value as a ratio between the detection output and the amplification degree by detecting the application voltage, and by converting the application voltage into the amplification degree using correlation data between the application voltage and the amplification degree which are stored in advance. According to this photometric device for emission spectroscopic analysis, unlike the device in the related art, it is not necessary to set sensitivity for each element in advance after estimating an amount of each element contained in a sample. JP-B-H06-68467 discloses that sensitivity adjustment can be fully automated and an excellent SN ratio can be maintained in a wider dynamic range.
JP-B-H06-68468 discloses an ICP emission spectrometer in which multiple samples whose concentration of analysis elements is changed at a substantially constant ratio are prepared, the respective samples are introduced into a plasma torch so as to emit light, which measures spectral intensity of the respective samples caused to emit the light in each negative high pressure by changing the negative high pressure applied to a photomultiplier, and which determines the correlation of a gain for each negative high pressure based on a measurement value of the spectral intensity of the respective samples. According to this ICP emission spectrometer, it is possible to accurately determine a gain calibration curve of the photomultiplier by adjusting concentration of an analysis sample. Thus, a light source lamp can be omitted. Therefore, JP-B-H06-68468 discloses that the ICP emission spectrometer can further reduce costs as compared to that in the related art.